It is normal in most hospitals today to provide in-room service of various medical gases such as oxygen, air, nitrous oxide, as well as a source of vacuum for suction equipment. The gases are generally provided, under pressure, at a central source, yet ready access is permitted throughout the hospital whenever needed. Central vacuum pumps similarly provide a source of vacuum whch is made available at utilization points in the hospital.
Service outlets are thus located at the point of ultimate use and are adapted to have an adapter "plugged in" to such outlets to cause the flow of gas, or vacuum, through the adapter to the end use. Most outlets are constructed to be operative as the adapter is inserted and to close-off automatically as the adapter is removed. One typical type of outlet is shown and described in U.S. Pat. No. 3,563,267 of Charles S. Thompson and which is of a double valve design having primary and secondary housings and corresponding valves.
The secondary housing is considered to be the roughing-in assembly and is installed in the hospital wall similar to electrical outlet boxes. The secondary housing is connected to the piping for the medical gas or vacuum and generally is provided with a check valve which is normally closed and which opens as the primary housing is inserted thereinto. Thus, the primary housing is removed for maintenance, etc. without leakage of gas or loss of vacuum.
The primary housing and secondary housing can be joined by a sliding seal to provide for differences in wall or plaster thickness.
In the U.S. Pat. No. 3,563,267 referred to, when the outlet is assembled with the primary housing engaged in the secondary housing, the secondary valve is open and the gas pressure, in particular, acts directly upon the primary valve which is located at the outermost point of the outlet and is immediately engageable by insertion of an adapter. Thus, the full line pressure of approximately 50 psi must be initially pushed against by an operator, such as a nurse, inserting the adapter. Some difficulties are thus experienced in the initial alignment and insertion of the adapter when immediately confronted with the force created by the line pressure.